Botanists discover 'remarkable' night-flowering orchid

The Bulbophyllum nocturnum is the first orchid species, out of about 25,000, to only flower at night

A night-flowering orchid, the first of its kind known to science, has been described by a team of botanists.

Experts say the "remarkable" species is the only orchid known to consistently flower at night, but why it has adopted this behaviour remains a mystery.

The plant was discovered by a Dutch researcher during an expedition to New Britain, an island near Papua New Guinea.

The findings appear in the Botanical Journal of the Linnean Society.

"It was so unexpected because there are so many species of orchids and not one was known [to flower] at night only," said co-author Andre Schuiteman, senior researcher and an orchid expert at the Royal Botanic Gardens, Kew.

"It was quite remarkable to find one, after so many years of orchid research, that is night-flowering," he told BBC News.

The specimen was discovered by co-author Ed de Vogel during a field trip in a region of lowland rainforest on the Pacific island.

One-night stand

Its unique flowering behaviour only came to light after the specimen was taken back to the Netherlands.

Dr de Vogel took the plant home in an attempt to understand why its buds appeared to wither when they reached a size that would normally produce 2cm flowers.

DAY OR NIGHT?

Although the tiny Bulbophyllum nocturnum is the first known night-flowering orchid, it is not uncommon for plants to flower at night. Most orchids though, flower both day and night.

The most famous night-flowering plant is the queen of the night cactus (Selenicereus grandiflorus) (see above). Each individual dinner plate-sized flower opens for one night per year (although each cactus can have several flowers). The blooms attract pollinating bats.

It is not clear exactly what pollinates Bulbophyllum nocturnum, but scientists think the job is carried out by nocturnal flies. Many night-flowering orchids are strongly scented in order to attract moths, but this orchid is the wrong shape and size for that.

The orchid family has evolved some special tricks to attract its pollinators. Many look like pollinating insects, in order to fool those insects into attempting to mate with them. Some even smell like rotten meat, which attracts flies.

To his surprise, he observed the flowers open a few hours after dusk and remain open until a few hours after sunrise.

The flowers opened for one night only, explaining why the buds appeared to be preparing to open one day, yet be withered the next day.

The specimen has been identified as belonging to the Bulbophyllum genus, which - with about 2,000 species - is the largest group in the orchid family.

While there are a number of orchids that do attract night-time pollinators, B. nocturnum is the first known species that exclusively flowers at night.

Mr Schuiteman said it still remained a mystery why the plant had developed such behaviour.

"We think related species are pollinated by tiny flies that think they are visiting fungi," he explained.

"The flowers mimic fungi, that's what the details of the flowers look like they do.

"The flies are looking for somewhere to lay eggs, and it is most probably [a species] that forages at night."

He added: "The orchid probably has a smell, not detectable by humans, to attract insects from a distance - and when they are nearby, the shape and physical aspects of the flower probably play a role too.

'Double-edged sword'

Mr Schuiteman said the exact reason why B. nocturnum only flowered at night would remain a mystery until further field studies had been completed.

Researchers speculate that the orchid is pollinated by tiny midge-like flies

However, time may be against them as the location in western New Britain where the original specimen was found lay within a logging area.

"It was previously inaccessible but now the area has been opened by logging," Mr Schuiteman said, adding that was an area that needed to be explored because there were probably many more species waiting to be described.

He said the logging activity was a double-edged sword because Papua New Guinea's government had granted logging licences in the area meant that it created roads that had allowed the plant hunters to carry out their exploration, yet it was an activity that could threaten the long-term survival of the species.

"My colleague who discovered it got permission from the logging company to go into the area, they even gave him a car to use.

"They realised that it would have been a shame to log the trees and destroy the orchids because they would be left lying on the ground exposed to full sunlight."

He called for areas to be left untouched: "It is the government that gives permits to log a particular area, so we should be asking them to protect areas and not issue permits for everything."